Control Synthesis Of Mesopous Alumina In The Presence Of Propylene Oxide

For this work,in water and non-aqueous?ethanol EtOH?systems without acid or base as pH modulators,mesoporous alumina materials with different structural characteristics have been synthesized under mild conditions by introducing propylene oxide?PO?as gel accelerator for the first time,inorganic aluminum salts as precursors,cationic quaternary ammonium salt surfactants?C_nTAB,n=12,14,16,18?and nonionic block copolymers?F127,F68,P123 and Brij56?as templates respectively,and the control and preparation rules of the materials were systematically studied by using various technologies such as XRD,N₂ adsorption,TG,SEM and TEM.The major findings are as follows:1?In the non-aqueous system composed of Al?NO₃?3·9H₂O-EtOH-C_nTAB-PO,the mesoporous alumina material with ?-Al2O₃ phase and a specific surface area of up to 456 m2/g was synthesized.It is found that the amount of PO plays an important role in the formation of mesoporous alumina,and the low PO content will make the system difficult to gel,and the excess amount of PO will make the reaction self-assembly process difficult to control and not be conducive to the formation of an ordered mesoporous alumina phase.By adjusting the PO/Al molar ratio,the pore size of the material can be adjusted in the range of 3.4 to 4.8 nm.Compared with the blanks without template,the introduction of the template will make specific surface area,pore capacity of the material significantly increased.The method was extended to the F127 template system,and the mesoporous ?-Al2O₃ with thermal stability up to 800? was obtained.By adjusting the type of template,the pore size of the material can be adjusted in the range of 4.6 to 7.8 nm.2?In the water system composed of Al?NO₃?3·9H₂O-H₂O-C_nTAB-PO,the mesoporous alumina material with ?-Al2O₃ phase and thermal stability up to 800?was synthesized.It was found that when the molar ratio of PO/Al was 3⁷,the concentration of template was in the range of 8.08¹9.47%,which would be more favorable for the synthesis of ordered mesoporous alumina.With the increase of the volume ratio of EtOH/H₂ O,the order of the samples is deteriorated.The change in the length of the alkyl chain has little effect on the pore size of the material.3?Interestingly,high thermal stability and highly ordered mesoporous ?-Al2O₃ materials was synthesized in the AlCl₃·6H₂O-H₂O-F127-PO system using open gelation.The material has a double mesoporous?3.8nm,6.2nm?pore structure and it is more conducive to the diffusion of matter.It was found that the order of the samples decreased with the increase of the amount of PO or EtOH,the concentration of the templating agent can be effectively adjusted in the range of 1.6 to 9.77%,but unfortunately the surface area of the material is low,the standard is only 65m2/g,it may be due to the partial closure of the mesopores in the process of roasting and releasing the template.Compared with the existing work,this work proposed the idea which the synthesis of mesoporous alumina was controlled by ring opening of propylene oxide,the synthesis process is not only more concise,efficient,environmental protection,but easy to achieve effective regulation of material structure and performance.It is expected that this synthetic idea can be further extended to the synthesis of other non-silicon-based mesoporous metal oxides,and more extensive expansion studies have been carried out.